This invention relates to a radio frequency identification (RFID) device for use in conjunction with a sheet fastener for document handling.
Inventory control benefits from the introduction of RFID systems used for items being transported, warehoused or sold. Such RFID systems have advantages over the short-range and line-of-sight limitations of bar code identification. An RFID system may include a reader and one or more tags. The reader may propagate a magnetic field or transmit an electric field carrier wave signal. A tag, located within the operating range of the reader and receiving the transmission, may transmit a response signal, which may be used by the reader to identify the tag's information.
An RFID tag may include an antenna, a transceiver and a transponder, and may be passive or active. The antenna may capture the energy from the reader's transmission. The transceiver of the RFID tag may read the transmission frequency of the signal from the reader. The transponder may include an integrated circuit containing the RF circuitry and information to be transmitted. The antenna, transceiver and transponder may be permanently attached and electrically connected to each other by epoxy and/or solder. Passive tags may absorb power received from the reader's transmission to power the circuit and transmit the response. Active tags may include a battery to provide power to operate the integrated circuit. The RFID tag may be associated with a variety of sensors to measure environmental conditions, such as current ambient or maximum exposed values in pressure, temperature, acceleration, navigation, etc. The sensors may be configured as micro-electronic mechanical systems (MEMS) to facilitate integration with the RFID tag.
In general, magnetic field systems may operate at about 125 kHz and over ranges of a few inches, with tag antennas comprising numerous turns of a fine wire around a core. More recent such systems may operate at 13.56 MHz over ranges of a few feet. Electric field systems may employ an antenna having a length of about half a wavelength of the operating frequency.
Passive transponders may be used at up to ultra high frequency (UHF) in the 860-930 MHz band at ranges of about 10 feet with relative temperature insensitivity. With simple integrated circuit and simple antenna and lacking onboard tuned circuits, passive UHF tags may be comparatively inexpensive in large quantities, and thus may require a complex reader to provide system energy, receiver selectivity and frequency stability. Active tags, having an internal power source for the integrated circuit, may be used for toll road applications at shorter ranges and higher microwave frequencies, such as 2.45 GHz and 5.8 GHz. The reader's high-energy field may activate the tag to send, receive, process and store data for the toll fees and the remaining balance. Beacon tags, also having an internal power source, may activate themselves at periodic intervals or when switched on before returning to inactive mode.
A plethora of passive tags in the vicinity of a reader may be used for tracking a high volume of items. Applications for such RFID tags have led to Electronic Product Code (EPC) specifications and tag manufacturing processes such as fluidic self-assembly by Alien Technology of Morgan Hill, Calif. EPC communication protocols of tags range in sophistication from Class 0 for read-only (factory programmable) to Class 4 for relay (inter-tag communication). Class 0 compliant tags may use electrically erasable programmable read-only memory (EEPROM), while Class 1 compliant tags may use write-once, read-many (WORM) capable chips.